Method of insulating underground pipe



May l0, 1955 D. c. GoFF METHOD DE INSULATING UNDERGROUND PIPE Filed June26, 1952 w114 [llamar/nana. A'

'fa-W States David C. Goti, La Grange, Ill., assignor to ZonoliteCompany, Chicago, ill., a corporation of Montana Application June 26,1952, Serial No. 295,786

9 Claims. (Cl. 154-28) The present invention is concerned with a methodoi insulating pipe carrying a heated uid, such as steam, hot Water,heated gases and other heated fluids.

One of the primary applications of the present invention is in the iieldof insulating steam pipes under conditions of extreme cold Where theground in which the steam pipes are to be imbedded is frozen,particularly in the so-called penna-frost egions.

In my previous Patent No. 2,355,966, issued August 15, 1944, I havedescribed an underground insulated pipe system in which undergroundpipes are imbedded in a monolithic mass of a heat insulating concretecomposition. In accordance with the processes of my prior patent, thepipes to be imbedded in underground systems are suspended over a base ofstructural concrete, and forms are provided about the suspended pipes toreceive the concrete pour. in using this system in arctic areas, theaqueous concrete composition may freeze, with resulting formation of iceparticles, thereby causing an irnproper setting of the concrete and asubstantially complete loss of the strength which the set concretecomposition is capable of attaining.

Another prime application of the invention other than in permanentlyfrozen soils, is in installation Where it is desired to keep steam orother heated fluids flowing continuously through the pipes or ductsduring the time that the insulation is being applied.

rl`he present invention provides a method for insulating pipes inunderground installation Without interruption of the flow of the heatediiuid carried by the pipes, while at the same time preventing freezingor boiling of the Water contained in the aqueous concrete compositionthat is poured about the pipes. In accordance with the present inventionsteam pipes, or other pipes or ducts carrying iiuid at a predeterminedelevated temperature are provided With a exible covering of a heatinsulating ma* terial prior to pouring of the heat insulating concretecomposition about the pipes. One of the features of the presentinvention is the control of the amount of heat lost from the heatediluid in the pipes to the aqueous concrete composition being pouredaround the pipes, the heat loss being so adjusted that suicient heat istransferred to the aqueous concrete composition to prevent freezing ofthe composition before its initial set, but insufficient to causeboiling of the water present in the concrete composition.

An object of the present invention is to provide a method for insulatingunderground pipes carrying steam or other heated fluids at predeterminedtemperatures.

- Another object of the present invention is to provide a method forinsulating steam pipes in underground installations withoutdiscontinuing the flow of the steam through the pipe during theapplication of the heat in` Sulating concrete embedding material of thehydraulic setting type.

Another object of the present invention is to provide a method forcontrolling the amount of heat loss from 2,707,984 Patented May it),i955 ice a steam carrying conduit to an aqueous, settable concretecomposition poured about the conduit.

Still another objectof the present invention is to provide an improvedmethod for achieving a controlled heat loss from a steam pipe to anaqueous concrete composition poured therearound, thereby preventingfreezing as Well as boiling of the Water contained in the aqueousconcrete composition.

A further description of the present invention will be made inconnection with the attached sheet of drawings in which:

Figure l is a fragmentary view with parts in elevation of an undergroundpipe system illustrating the support means and the heat insulating meansemployed;

Figure 2 is a cross-sectional view With parts in elevation takensubstantially along the line II-ll of Figure 1; and

Figure 3 is a view similar to Figure 2, but illustrating the structurewhen the heat insulating concrete material has been poured around theunderground pipe insulation and has been set into an integral monolithicstructure.

As shown on the drawings:

As shown in Figures l and 2, the process of the present inventioninvolves providing a duct or pipe 1t) through which steam or otherheated iluid at a predetermined temperaturc is being passed. To providefor a controlled amount of heat loss from the steam flowing from thepipe 10, the pipe l@ is covered with a ilexible, heat insulatingmaterial which may be a batt l1 of glass wool, or similar insulatingmaterial wrapped in one or more layers 11a around the periphery of thepipe l@ as illustrated in Figure 1. Any type of liexible or rigid typeinsulating covering for the pipe may be used for this heat loss control.For example, a rigid pre-formed cylinder or segmented cylinder ofinsulating material may provide a heat insulating jacket of the properheat transmitting characteristics. Such a rigid insulator may, forexample, be composed of foam glass sections or an asbestos board.

The particular amount of heat insulating material 11 to be used in anygiven insulation will depend primarily upon the diameter of the steampipe l0 and the temperature of the pipe` lil. Knowing the temperature,heat transfer characteristics of the insulating material and thequantity of heat insulating concrete to be poured about the steam pipeenables one to calculate the thickness of insulating material to be usedin any given installation. As previously mentioned, other heatinsulating materials besides glass Wool may be employed, although thelatter is preferred. Other insulating materials include paper,corrugated paper, and rock Wool.

The supporting members for holding the pipe 10 in position inunderground installation are a series of support blocks 12 on which thejaclteted steam carrying pipe 1G rests. The blocks 12 are bottomed on abase 14 or" structural concrete previously laid in the excavation. Thesupport blocks 12, as Well as the concrete composition used to insulateand imbed the steam line, are preferably composed of the compositionsdescribed in my aforementioned Patent No. 2,355,966. As described inthis patent, a suitable mixture contains about one bag of Portlandcement (Weighing about 94), 8 cubic feet of expanded vermiculite of aparticle size from minus 10 to plus 65 mesh, 7 quarts of a stabilizedasphalt emulsion and 26 gallons of water. The asphalt emulsion may beprepared by mixing approximately 55 parts by weight of 50 to 60penetration asphalt from California crude petroleum With about 43.35parts of hot water containing about 0.15 part of caustic soda to producea quick-breaking emulsion. For the purposes of the present invention,

the asphalt emulsion is converted to the slow-breaking' Vinsol" resin,the latter being a blackresidue remaining after extracting crude woodrosin with petroleum solvents.

After the pipe 1G is wrapped with the heat insulating material andpositioned along the spaced support blocks 12 the forms in which thepipes 10 are disposed may be filled with an Iaqueous concretecomposition which is settable into a heat insulating, lightweightcomposition. l prefer to use for this purpose the aforementionedconcrete composition containing substantial amounts of exfoliatedvermiculite as this type of concrete composition has several uniqueadvantages for this type of installation. Concrete compositions of thistype have good elasticity, workability and plasticity and in addition,after the concrete has been properly set, it can be subjected torepeated cycles of freezing and thawing without breaking up, cracking ordisintegrating the concrete structure. Further, a heat insulatingconcrete of this type is quite water repellent and has low capillarity.Further, the heat insulating concrete is lightweight, inert andnoncorrosive, thereby eliminating any danger of deterioration, rotting,molding or disintegration. In addition, such concrete is fire-proof andwill safely withstand temperatures up to 2000 F.

In addition to or in place of vermiculite other lightweight aggregatessuch as pearlite, pumice, slag and the like may be employed for the samepurpose. As a further` alternative insulating concrete containing noaggregate and produced by aerating neat cemcnts may be employed for thepurposes of the present invention.

As shown in Figure 3, after the aqueous heat insulating concretecomposition is poured into the form about the pipe 10 on its supports12, the concrete composition will set into a lightweight, monolithicmass 13 surrounding the pipe 1G and the support blocks 12. By the properadjustment of the amount of heat insulating material 11 about thesurface of the pipe 10, the concrete composition will undergo a more orless normal drying period without the formation of ice particles andwithout overheating of the water present in the concrete composition.Furthermore, drying of the concrete due to the flow of heat from theheated pipe 1t) through the heat insulating Wrap 11 can be so controlledas to require only a minimum drying out period, since the drying takesplace from the inside of the mass outwardly. In case the pipe 10 is usedas a steam pipe, steam is continuously pasesd through the pipe 10 fromthe start of the pouring operation until the concrete in the monolithicmass has completely set. As previously stated, the amount of heat lossfrom the pipe 10 through the insulating material 1l is regulated inaccordance with the governing factors, including the outsidetemperature, so as to prevent the formation of ice crystals and yet notheat the water present in the concrete composition sufciently to causeexcessive vaporization of the water. Consequently, the concrete sets ina relatively short time into an integral, monolithic mass of substantialstrength and good heat insulating properties.

lt will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

l claim as my invention:

l. A method of insulating an underground pipe which comprises applying afirst heat insulating material about the periphery of said pipe, passinga heated fluid through said pipe and pouring an aqueous composition of asecond insulating concrete about said pipe, said first heat insulatingmaterial about said pipe being of such insulating value as to providesufcient heat loss to said aqueous composition to permit setting of saidconcrete without freezing of the water contained in said compositionwhile providing insuicient heat transfer from said heated fluid to saidaqueous composition to cause excessive vaporization of the water in saidaqueous composition.

2'. A method of insulating an underground pipe which comprises applyinga flexible heat insulating material about the periphery of said pipe,passing a heated fluid through said pipe and pouring an aqueouscomposition of an insulating concrete about said pipe, the amount ofsaid heat insulating material about said pipe being of such insulatingvalue as to provide sufficient heat loss to said aqueous composition topermit setting of said concrete without freezing of the water containedin said composition while providing insuicient heat transfer from saidheated uid to said aqueous composition to cause excessive vaporizationof the water in said aqueous composition.

3. A method of insulating an underground pipe which comprises applying anon-flexible heat insulating material about the periphery of said pipe,passing a heated fluid through said pipe and pouring an aqueouscomposition of an insulating concrete about said pipe, the amount ofsaid heat insulating material about said pipe being of such insulatingvalue as to provide suflicient heat loss to said aqueous composition topermit setting of said concrete without freezing of the water containedin said composition while providing insufficient heat transfer from saidheated fiuid to said aqueous composition to cause excessive vaporizationof the water in said aqueous composition.

4. The method of insulating an underground pipe which comprises applyinga heat insulating material about the periphery of said pipe, supportingsaid pipe along spaced support blocks composed of a heat insulatingmonolithic concrete material, passing a heated iiuid through said pipe,and pouring an aqueous composition of insulating concrete about saidpipe, said heat insulating material being present in suiiicient quantityto provide sufiicient heat loss to said aqueous composition to permitsetting of said concrete without freezing of the water contained in saidcomposition whiie providing insufficient heat transfer from said heatedfluid to said aqueous composition to cause boiling of the water in saidaqueous composition.

5. The method of insulating an underground pipe which comprises wrappinga layer of glass wool about the periphery of said pipe, passing a heatediiuid through said pipe, and pouring an aqueous composition ofinsulating concrete about said pipe, the layer of said glass wool aboutsaid pipe being of such thickness as to provide sufcient heat loss tosaid aqueous composition to permit setting of said concrete withoutfreezing the water contained in said composition, while providinginsufficient heat transfer from said heated iiuid to said aqueouscomposition to cause excessive vaporization of the water in said aqueouscomposition.

6. The method of insulating an underground pipe which comprises wrappinga layer of glass wool about the periphery of said pipe, passing a heatedfluid through said pipe, pouring an aqueous composition of insulatingconcrete about said pipe, and setting said concrete into a monolithicstructure, said glass wool being present in such thickness as to providesufficient heat loss to said aqueous composition to permit setting ofsaid concrete without freezing the water contained in said composition,while providing insumcient heat transfer from said steam to said aqueouscomposition to cause boiling of the water in said aqueous composition.

7. The method of insulating an underground pipe which comprises wrappinga layer of glass wool about the periphery of said pipe7 supporting saidpipe along spaced support blocks of a heat insulating monolithicconcrete material, passing a heated uid through said pipe and pouring anaqueous composition of insulating concrete about said fluid heated pipe.

8. The method of laying a pipe comprising the steps of Wrapping the pipewith an insulating material, positioning said pipe on supports of asecond insulating material, and passing a heated uid through the pipewhile pouring an aqueous composition of said second insulating materialabout said first insulation to maintain said boiling point to facilitatedrying of said insulating mateaqueous composition at a temperature aboveits freezing rial without freezing. point and below its boiling point.

9. The method of laying an insulated pipe at or below References Citedin the fue 0f this Patent freezing temperatures comprises the steps ofpositioning said pipe on supports of an insulating material and passinga heated material through the pipe While pouring an yae; DIES 56 aqueouscomposition of said insulating material about 1797443 Povelel Mag' 241931 said plpe, thereby mauitainmg said aqueous composition 2,312,993Stephens Mar. 2, 1943 at a temperature above its freezing point andbelow its 10

7. THE METHOD OF INSULATING AN UNDERGROUND PIPE WHICH COMPRISES WRAPPINGA LAYER OF GLASS WOOL ABOUT THE PERIPHERY OF SAID PIPE, SUPPORTING SAIDPIPE ALONG SPACED SUPPORT BLOCKS OF A HEAT INSULTING MONOLITHIC CONCRETEMATERIAL, PASSING A HEATED FLUID THROUGH SAID PIPE AND POURING ANAQUEOUS COMPOSITION OF INSULATING CONCRETE ABOUT SAID FLUID HEATED PIPE.